Dr. Gordon Feldman, Johns Hopkins physicist

Dr. Gordon Feldman, a Johns Hopkins physicist who contributed to discovery of the antiproton, died in his sleep Wednesday at Symphony Manor Assisted Living from complications of Alzheimer's.

The Baltimore resident was 85.

The son of a street peddler and homemaker grew up the youngest of six children in Windsor, Ontario, Canada.

Dr. Feldman received a full scholarship to study at University of Toronto in Canada and graduated with a bachelor's degree in physics in 1950. He was the first in his family to attend college.

He had intended to study classics but changed his major after inspiration from a physics professor, his son Leonard Feldman, said. He earned his master's and doctorate in the field from the University of Birmingham, England.

Dr. Feldman would go on to become a prominent expert in theoretical physics, which uses mathematics, rather than experiments, to explain the workings of the world.

"There was a purity in that kind of science that he loved; the complicity and intricacy that it involved," his son said.

He came to the United States in 1955 to do his post-doctoral work at the Institute for Advanced Study in Princeton, N.J. A year later he began his career at the Johns Hopkins University as an associate professor. He stayed for nearly five decades, rising to the ranks of full professor and emeritus professor upon retiring in 1998.

His son remembers his father's office adorned with wall-to-wall chalkboards that he and his colleagues would fill with mathematical equations and formulas.

Dr. Feldman took frequent sabbaticals to conduct research and teach at other universities, including Imperial College in London from 1968 to 1969 and 1974 to 1975. He received a John Simon Guggenheim Memorial Foundation Fellowship that he used for research in London from 1962 to 1963 and was a Royal Society Guest Research Fellow at the University of Cambridge from 1984 to 1985.

While at Imperial College, Dr. Feldman worked for J. Robert Oppenheimer, a nuclear physicist who helped create the first atomic bomb. During a stint at Imperial College, mutual friends also introduced him to Janet Robson. The two married on March 23, 1968. He brought his new wife and her two children from a previous marriage, Joanna Kelly and Matthew Kelly, back to Baltimore. Four years later Leonard was born.

Colleagues recall Dr. Feldman as a brilliant but humble man who made many contributions to the advancement of physics.

"He would have been better known if he had advertised more extensively," said Gabor Domokos, professor emeritus of physics at Johns Hopkins University. "He was a very modest person, but he was extremely good."

Dr. Feldman played a behind-the-scenes role in the discovery of the antiproton, a proton with a negative electric charge. When scientists at the University of Berkeley in California thought they needed a high-energy threshold to generate an anti-proton, Dr. Feldman showed them they could use a lower threshold.

Other colleagues described Feldman as a mentor to students and a patient man who could break down physics for the average person to understand.

"He was a deep thinker and theoretical resource," said Aihud Pevsner, a specialist in high energy physics who worked with Feldman at Hopkins. "Everybody came for his advice when they had trouble understanding theoretical physics."

Dr. Feldman was a longtime resident of Roland Park who indulged in classical music, opera and Colts and Ravens football. He also enjoyed going to the theater and traveling to exotic locations. The family once took a ship from New Zealand to Seattle and traveled the South Pacific where they fed the sharks and lived in a thatched-roof house overlooking the water.

"He was a big jokester," said wife Janet. "He loved his family and was always smiling."

Dr. Feldman is survived by his wife and three children, Joanna Kelly of Jarrettsville, Matthew Kelly of Pembroke Pines, Fla., and Leonard Feldman of New York. A memorial service is being planned in his honor.